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    • HERS RATER WRITTEN EXAM >
      • Section 1 Building Science Fundamentals >
        • 1a. Basic Terms & Definitions >
          • 1. Airflow in Buildings
          • 2. Equipment Efficiencies
          • 3. Power and Energy
          • 4. Effective Leakage Area
          • 5. Area Weighted R-Value
          • 6. Baseload / Seasonal Energy Use
          • 7. Driving Forces (Including Natural and Mechanical)
          • 8. Behavior of Radiation
          • 9. Thermal Resistance / Transmittance: R and U Values
          • 10. Latent / Sensible Heat
          • 11. Total Equivalent Length
          • 12. Dehumidification / Humidification
          • 13. Convert Pressure Units
          • 14. Thermal Bridges
          • 15. Pressure Boundary
          • 16. Stack Effect
          • 17. Exfiltration and Infiltration
          • 18. Natural / Mechanical Ventilation
          • 19. Net Free Area
          • 20. Input & Output Capacity
          • 21. Peak Electrical Demand
          • 22. Permeability and Perm Rating
          • 23. Standby Loss
          • 24. IAQ (indoor air quality): Moisture, CO, Dust
        • 1b. Principals of Energy, Air & Moisture Thermodynamics >
          • 1. Thermodynamics: Conduction, Convection, Radiation, ΔT
          • 2. Factors That Affect Insulation Performance
          • 3. House Pressurization/Depressurization by Various Forces
          • 4. Heat Gain / Loss
          • 5. Power and Energy
          • 6. Moisture Transport Mechanisms
          • 7. Identify Areas of Highest Relative Humidity
          • 8. Principles of Combustion
        • 1c. Combustion Safety >
          • 1. Combustion Analysis
          • 2. Carbon Monoxide (CO) Testing
          • 3. Combustion Appliance Venting, Draft, Combustion Air & Sizing
          • 4. Understand Combustion Safety Issues
      • Section 2 Buildings and Their Systems >
        • 2a. Building Components >
          • 1. Identify basic duct configurations and components
          • 2. Identify Basic Hydronic Distribution Configurations and Components
          • 3. Identify Basic Structural Components of Residential Construction
          • 4. Thermal Boundaries and Insulation Applications
          • 5. Basic Electrical Components and Safety Considerations
          • 6. Basic Fuel Delivery Systems and Safety Considerations
          • 7. Basic bulk water management components (drainage plumbing gutters sumps etc)
          • 8. Vapor barriers/retarders
          • 9. Radiant Barrier Principles and Installations
          • 10. Understand Fenestration Types and Efficiencies
          • 11. Understand Issues Involved With Basements, Crawlspaces, Slabs, Attics, Attached Garages, Interstitial Cavities, and Bypasses
          • 12. Understand Issues Involved With Ventilation Equipment
          • Understand Basic Heating / Cooling Equipment Components Controls and Operation
          • Understand Basic DHW Equipment Components Controls and Operation
          • Identify Common Mechanical Safety Controls
          • Identify Insulation Types and R-Values
          • Understand Various Mechanical Ventilation Equipment and Strategies: Spot, ERV, HRV
        • Conservation Strategies >
          • Appropriate Insulation Applications and Installation Based On Existing Conditions
          • Opportunity for ENERGY STAR Lighting and Appliances
          • Identify Duct Sealing Opportunities and Applications
          • Understand Importance of Air Leakage Control and Remediation Procedures
          • Blower Door-Guided Air Sealing Techniques
          • Water Conservation Devices and Strategies
          • Domestic Hot Water (DHW) Conservation Strategies
          • Heating & Cooling Efficiency Applications
          • Proper Use of Modeling to Determine Heating and Cooling Equipment Sizing and Appropriate Energy
          • Understand the Use of Utility History Analysis in Conservation Strategies
          • Appropriate Applications For Sealed Crawlspaces Basements and Attics
          • Identify / Understand High Density Cellulose
          • Appropriate Applications for Fenestration Upgrades Including Modification or Replacement
        • Comprehensive Building Assessment Process >
          • Determine Areas of Customer Complaints / Concerns in Interview
          • Understand / Recognize Need For Conducting Appropriate Diagnostic Procedures
          • Interaction Between Mechanical Systems, Envelope Systems and Occupant Behavior
        • Design Considerations >
          • Appropriate Insulation Applications Based On Existing Conditions
          • Understand Fire Codes as Necessary to Apply Home Performance in a Code-Approved Manner
          • Understand / Recognize Building Locations Where Opportunities for Retrofit Materials
          • Understand Climate Specific Concerns
          • Understand Indoor Environment Considerations for the Environmentally Sensitive
          • Understand Impact of Building Orientation, Landscape Drainage, and Grading
          • Opportunity Potential Renewable Energy Applications: Geothermal, Photovoltaic, Wind
          • Understand Impact of Shading on Heating / Cooling Loads
          • Awareness for Solar Gain Reduction / Solar Gain Opportunities
          • Understand Need for Modeling Various Options For Efficiency Upgrades
      • Measurement & Verification of Building Performance >
        • Measurement & Verification of Building Performance >
          • Air Leakage Test Results
          • Understand Building Shell / Envelope Leakage
          • Apply Fundamental Construction Mathematics and Unit Conversions
          • Calculate Building Tightness Levels (Minimum Ventilation Requirements)
          • Calculate Heating Degree Days and Cooling Degree Days
          • Identify Proper Appliance and Combustion Appliance Venting
          • Ventilation calculations and strategies
          • Proper methods for identifying / testing fuel leaks
          • Blower door setup, accurate measurement and interpretation of results
          • Combustion Appliance Zone (CAZ): depressurization, spillage, draft, Carbon Monoxide (ambient and flue)
          • Carbon Monoxide (CO) evaluation: ambient
          • Proper applications and use of temperature measuring devices
          • Pressure pan and room to room pressure diagnostics
          • Recognize contributing factors to comfort problems
          • Inspect for areas containing moisture or bulk water in undesirable locations
          • Understand and inspect for basic electric safety (e.g. frayed wires, open boxes, etc)
      • RESNET HERS RATER National Standards & Project Specifications >
        • Understand applicability content and intent of BPI National Standards – Do no harm, make buildings more healthy, comfortable, durable and energy efficient
        • Recognize need for a professional local/state/national codes evaluation
        • Be able to specify appropriate materials and processes needed for building performance projects
      • Analyzing Buildings Systems >
        • Recognize need for air sealing measures and their impact on other building systems
      • Conduct and Communications >
        • Conservation strategies
        • Conservation strategies
    • HERS RATER FIELD EXAM >
      • How To Put The House Under Worst Case & CAZ
      • What's What? Pa, CFM, CFM50, CAZ, Draft, Room Pressure
      • What To Know In The Attic
      • What To Know In The House
    • BLOWER DOOR TEST >
      • Manometer Setup
    • RESNET STANDARDS >
      • RESNET Standards Decoded
  • ESSENTIALS
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    • COMMON AUDITOR / CREW MISTAKES
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Building Science Fundamentals

Understand Building Shell / Envelope Leakage As A
Function Of Pressure Difference And The Size Of Holes In
The Air Barrier

Understand Building Shell / Envelope Leakage As A
Function Of The Pressure Difference

Understand Building Shell / Envelope Leakage As A
Function Of The Size Of Holes In The Air Barrier

Using the effective leakage area, you can get a rough idea of how big the hole is you are trying to seal.  The effective leakage area says that for every 1000 CFM50, there's about one square inch of leakage area in the envelope. Then compare that to how big you want the hole to be using ASHRAE standards for ventilation and the MVR.  The difference between the two will tell your crew how much air leakage should be done in understandable terms.

Some examples of using this technique are below.

  1. You find the CFM50 of a home is 2350 CFM50 with all windows closed and interior doors open.  With the blower door still running at 50 Pa, disconnect the manometer and leave one tube connected to A or B.  Then place the tube in a bedroom or room of choice and close the door.  You record a pressure reading of 15 Pa, open the door and repeat the steps under all the doors to get pressure readings of 5 Pa, 7 Pa and 2 Pa.  These numbers will give you an idea of what room has more air sealing opportunities than others with the high numbers signaling more air leakage.
  2. You find the CFM50 of a home is 6350 CFM50 with all windows closed and interior doors open. This means that you have approximately a 6350 / 10 = 635 sq inch window open in the home.  So lets find where that 635 sq inches is coming from.  In the attic you discover a small 1" x 1" hole where an electrical wire goes into the home.  Seal that up and you'll be down to 634 sq inch of leakage.  You continue and you find the following: 10 accessible 1x1 sq in holes from electrical wires and a 12"x12" open wall cavity.  Add those areas up and you can potentially seal a 22x22 sq in hole or a 484 sq inches.

Next Section

3a. Applied diagnostics and troubleshooting
  1. Application of measured air leakage test results 
  2. Understand building shell/envelope leakage as a function of pressure difference and the size of holes in the air barrier 
  3. Apply fundamental construction mathematics and unit conversions 
  4. Calculate building tightness levels (minimum ventilation requirements) 
  5. Calculate heating degree days and cooling degree days 
  6. Identify proper appliance and combustion appliance venting 
  7. Ventilation calculations and strategies 
  8. Proper methods for identifying / testing fuel leaks 
  9. Blower door setup, accurate measurement and interpretation of results 
  10. Combustion Appliance Zone (CAZ): depressurization, spillage, draft, Carbon Monoxide (ambient and flue) 
  11. Carbon Monoxide (CO) evaluation: ambient 
  12. Proper applications and use of temperature measuring devices 
  13. Pressure pan and room to room pressure diagnostics 
  14. Recognize contributing factors to comfort problems 
  15. Inspect for areas containing moisture or bulk water in undesirable locations 
  16. Understand and inspect for basic electric safety (e.g. frayed wires, open boxes, etc) 
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